Mobility and broadband has become a development trend of modern communication technologies, and how to alleviate influences of co-channel interference, multi-access interference and multi-path fading has become a predominant factor considered while improving the performance of a wireless mobile communication system. In recent years, an intelligent antenna technology has become a study hotspot in the field of mobile communications.
The smart antenna technology brings a significant advantage to a mobile communication system. For example, smart antennas are used in connection with other baseband digital signal processing technologies, e.g., joint detection, interference cancellation, etc., and with the use of the smart antenna technology in a wireless base station, the base station receives a signal which is the sum of signals received by respective antenna elements and receivers, and if a maximum power integration algorithm is adopted, the total received signal will be improved by 10*1gN dB without considering multi-path propagation, where N is the number of antenna elements. With the presence of multiple paths, this improvement of reception sensitivity will vary with a multi-path propagation condition and an uplink beam forming algorithm and may also approach a gain of 10*1gN dB.
At present, the smart antenna technology has become one of primary trends in the development of communication technologies at the physical layer. The smart antenna technology can be applied not only in a Time Division Duplex (TDD) system but also in a Frequency Division Duplex (FDD) system, and wide applications of smart antennas have offered us a leading and perfect technology platform over which the development of mobile communication technologies has been impelled to some extent.
Smart antennas are applied particularly in a mobile communication system, for example, in a TD-SCDMA (Time Division-Synchronization Code Division Multiple Access) system with an 8-element smart antenna array with 8 element antenna ports and 1 calibration port and the antennas are installed by connecting nine cables including a calibration cable. The presence of the plurality of antennas necessitates calibration of the antennas in a practical network. In an existing antenna calibrating technology, a calibration period is set manually, and it is impossible to report in real time the presence of the differences of amplitudes and phases of respective radio frequency channels after the calibration. If the differences of the amplitudes and the phases of the radio frequency channels last for a long calibration period, there may be a strong influence on downlink beamforming, particularly beamforming of a broadcast channel, thus resulting in broadcast beam distortion and failing to satisfy required beamforming of 65+/−5 degrees for network planning.
An existing antenna calibrating method typically includes the following steps:
a calibration period is set; a reception calibration sequence is transmitted at a baseband and a reception calibration coefficient CRX is calculated; a transmission calibration sequence is transmitted at a baseband and a transmission calibration coefficient CTX is calculated; and it is determined, according to a calibration period, whether to perform next reception calibration and transmission calibration, the CRX and CTX are used in this calibration period.
The existing antenna calibrating technology generally has the following two disadvantages.
(1) Calibration precision cannot be fed back, and therefore such a condition cannot be monitored that there is still a difference of a radio frequency channel after the calibration.
(2) The calibration period cannot be adjusted in real time according to the calibration precision by shortening the calibration period for a rapidly varying radio frequency channel or lengthening the calibration period for a slowly varying radio frequency channel.
Therefore, it is necessary to propose such a technical solution that the difference of the radio frequency channel can be monitored in real time through calibration error parameters and the calibration precision can be inspected in real time by reporting the calibration error parameters and a calibration period can be adjusted in real time according to the calibration error parameters by shortening the calibration period for a rapidly varying radio frequency channel or lengthening the calibration period for a slowly varying radio frequency channel.